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# Anti-amyloid monoclonal antibodies

Antibodies that clear amyloid plaques from the brain in early Alzheimer disease. They slow decline but do not cure, and need MRI checks for ARIA.

Updated Nov 1, 2026

## What they are

Lecanemab and donanemab are monoclonal antibodies against amyloid beta (Aβ), the peptide that builds the plaques of Alzheimer disease. They are the first treatments aimed at the disease process rather than at symptoms, and they are used only at the mild cognitive impairment or mild dementia stage.

## Mechanism of action

The antibody binds aggregated Aβ in the brain and lowers the plaque load. Removing amyloid early slows clinical decline modestly; it does not restore lost neurons. The same action on amyloid in vessel walls explains their typical adverse effect, amyloid-related imaging abnormalities (ARIA).

Target: Aggregated amyloid beta (Aβ)

## Key points

- Only for early Alzheimer disease (mild cognitive impairment or mild dementia) with amyloid confirmed by amyloid PET or cerebrospinal fluid tests.
- Boxed warning for ARIA: brain oedema (ARIA-E) and microhaemorrhages (ARIA-H); usually silent and reversible, rarely severe with seizures.
- ApoE ε4 homozygotes have more ARIA, including serious ARIA: ApoE genotype is tested before treatment.
- MRI before starting and during treatment; anticoagulants raise the risk of intracerebral haemorrhage.
- Infusion-related reactions and hypersensitivity (angioedema, anaphylaxis) can occur.

## Drugs in this class

- [**Lecanemab** Monoclonal antibody against amyloid beta for early Alzheimer disease. It slows decline; its main risk is brain… Aggregated amyloid beta (Aβ), cleaved from amyloid precursor protein](https://durgical.com/en/pharmacology/lecanemab/)
- [**Donanemab** Intravenous anti-amyloid antibody for early Alzheimer disease. It lowers plaques and slows decline; ARIA and headache… Amyloid beta (Aβ) in amyloid plaques](https://durgical.com/en/pharmacology/donanemab/)

## Others in the class

- Aducanumab

## Test yourself

Think of the answer, then tap the question to see it.

## At which stage of Alzheimer disease are anti-amyloid antibodies started?

Mild cognitive impairment or mild dementia, with amyloid pathology confirmed; there are no data for starting earlier or later.

## What are ARIA-E and ARIA-H?

Amyloid-related imaging abnormalities: oedema (E) and microhaemorrhages or small bleeds (H), seen on MRI.

## Which genotype is tested before treatment, and why?

ApoE ε4: homozygotes have a higher incidence of ARIA, including symptomatic and serious ARIA.

## Which drug group needs special caution with these antibodies?

Anticoagulants, because they were associated with more intracerebral haemorrhages.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [FDA Converts Novel Alzheimer’s Disease Treatment to Traditional Approval](https://www.fda.gov/news-events/press-announcements/fda-converts-novel-alzheimers-disease-treatment-traditional-approval) (U.S. Food and Drug Administration, 2023); [FDA approves treatment for adults with Alzheimer’s disease](https://www.fda.gov/drugs/news-events-human-drugs/fda-approves-treatment-adults-alzheimers-disease) (U.S. Food and Drug Administration, 2024); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=N06DX) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/classes/anti-amyloid-monoclonal-antibodies/